The present invention relates in general to an optical transmission and receiving module which is connected to an optical transmission path such as an optical fiber at an end thereof for transmitting (or sending) and receiving an information signal. More particularly, the invention is concerned with an optical transmission module which includes a light emitting device and a light receiving device (photodetector) disposed within a single package for performing a bidirectional transmission of information or data. Further, the invention is also concerned with an optical communication system in which the optical transmission and receiving modules mentioned above are employed.
In an optical transmission system such as typified by an optical communication system in which an optical transmission path constituted, for example, by an optical fiber cable (hereinafter, the optical transmission path will also be referred to as the optical fiber for convenience of description), there is employed a bidirectional optical transmission module (hereinafter referred to as the optical module for simplification of description) as a terminal for transmission and reception of information, a typical structure of which is disclosed in, for example, JP-A-62-229206. This prior art optical module is comprised of a light emitting device, a collimator lens for collimating light emitted from the light emitting device, a light receiving device (photodetector), a condenser lens for coupling a light beam to the light receiving device, a common-port lens for collimating a light beam emitted from an end face of an optical fiber, and a penta-prison block provided with a filter for branching or multiplexing with respect to wavelength of light, wherein the components mentioned above are accommodated within a single metal casing.